A Writer's Bookshelf: Gray's Anatomy
There are a ton of source books to look at that detail the anatomical systems of the human body, but everyone always comes back to Gray's Anatomy as a first base source. If you go down the isles of a book store or library, you can find tons of books with drawings, descriptions, diseases, you name it, all dealing with the body. The key here is not to get them all, but to choose the resource that is best for your writing and your needs.
Gray's Anatomy is a good catch all basics. And note that I use the word "basics" loosely here. Anything doing with human anatomy is not basic at all. There are so many different systems and symptoms and so forth that you can get lost without a good guide to keep you on tract. Again, choose the source that is right for you. I have one at home that is a book of ailments and symptoms. I've seen one on plagues throughout the ages (real happy stuff). Remember, in the end, look for the book that best suits you, remembering that you can always go to the library and find another one if you need it. Just don't tell the librarian that you're looking for a novel to help you dismember a body...they don't get it...